If you want to use the CSV MIME-type? in PHP. You could try to force the browser to open a “Save As…” dialog by doing something like:
echo "cell 1, cell 2";
Which should work across most major browsers.
If you like this question & answer and want to contribute, then write your question & answer and email to freewebmentor[@]gmail.com. Your question and answer will appear on FreeWebMentor.com and help other developers.